Copper (Cu) is an essential yet dangerous element at high concentrations for plant growth as well as for human health after it enters the food chain. Cu comes from the mining of waste and creates a problem for plants in the soil. Cu tolerant bacteria may help to reduce Cu uptake by the plant and mitigate the effect of Cu on the gas exchange parameters, Cu uptake of plant. This study was planned to study the effect of Cu tolerant bacteria on the earthworm activity, Cu uptake, and physiological parameter of the mung bean crop. Three Cu tolerant bacterial strains SC1, SC2, and SC3 at two Cu levels 0 and 150 mg kg^-1 of soil were used. Results showed that Cu application reduced the AChE assay for earthworm activity, increased the Cu uptake both in root and shoot but Cu uptake was more in root compared to shoot. Physiological gas exchange parameters were negatively affected by Cu application. Cu application at 150mg kg^-1 soil reduced the earthworm activity (31%) compared to the control. Cu tolerant bacterial strains inoculum improved the gas exchange parameters photosynthetic rate (43%), transpiration rate (48%), stomatal conductance (39%), substomatal conductance (34%), and total chlorophyll content (28%) while reducing the uptake of Cu in the shoot (24%) and root (26%) compared to 150 mg Cu kg^-1 of the soil application treatment. It is concluded that the use of Cu-tolerant bacterial strains as inoculum can help improve the chemical status and gas exchange parameters of crops grown in Cu-contaminated soils.

Keywords: Cu contaminated soils, Cu tolerant bacteria, Gas exchange parameters, Earthworm activity